ABSTRACT: Several lines of evidence indicate that drinking behavior in women is more likely to be motivated by affect regulation and stress, whereas drinking in men is motivated by stimulation and alcohol-related positive reinforcement. Project 3 will collect preliminary data for a Phase 2b double-blind, placebo-controlled, parallel-group study to examine sex differences in guanfacine's effect on 1) counteracting stress- and stimulation-based drinking behavior in the laboratory and 2) improving clinical outcomes during a subsequent treatment phase.